As electronic equipments are getting smaller, thinning of a copper conductor has been required and oxygen-free copper excellent in ductility and processability has been increasingly used. Thus, a method of producing oxygen-free or low-oxygen copper wire rods through a belt & wheel type continuous casting and rolling high in production capacity has been proposed.
Meanwhile, it is known that a precipitation strengthening copper alloy, e.g., a Corson alloy, is remarkably brittle at an intermediate temperature. Therefore, it has been pointed out that there is a need to avoid cracks upon casting. In addition, the heating conditions before hot-rolling have to be also considered sufficiently.
Further, when the copper alloy containing a trace amount of Si or Mg is cast through the belt & wheel type continuous casting and rolling method, alloying elements are naturally oxidized and thus a large amount of slag is occurred, thereby making it difficult to produce the wire rod.
For those reasons, it has been a current state of the art that, when producing the Corson-based alloy wire rod, an ingot is first produced through low-speed casting or semi-continuous casting with a very precise cooling control, and then the resultant ingot is processed through hot working while performing the control of a temperature increasing rate and the like.
In addition, since sulfur (S) that is inevitably contained in copper alloys encourages the intermediate temperature brittleness, a trace amount of Mg, Mn, Zn, and the like is added to the copper alloy, to stabilize the sulfur and thus to prevent the intermediate temperature embrittlement.
Further, although the production of the Corson-based alloy wire rod using a movable mold has been proposed and attempted, the precipitation progresses as a quenching temperature is lowered and thus electric conductivity of the copper alloy wire rod is made high. This means that the original performance cannot be exhibited because there is short of Ni or Si required for fine precipitation contributing to strength enhancement in an aging heat treatment. In order to improve this phenomenon, there is a need to perform a solution treatment for the copper alloy wire rod, which has gone through rolling, at a high temperature for a long period of time. This results in a huge increase of the production costs for the copper alloy wire rod.